While the amount and type of fats (saturated vs unsaturated), carbohydrate (starches vs sugars) and even protein (animal vs vegetable) required for good health and longevity are at times fiercely debated, most nutrition experts agree that dietary fibre is beneficial to human health and that most of us need to eat more.
It’s generally agreed that we need to consume at least 3.3 grams of fibre for every 1000 kJ (240 calories) of energy that we consume each day – for an average woman that’s 25 grams a day; and 30 grams a day for an average man.
Few people achieve this because most don’t consume enough fruit, vegetables, legumes and wholegrains – the natural sources of dietary fibre. In Australia, we only consume around 2.5 grams per 1000 kJ and fibre intakes appear to be dropping from 23.1 grams a day in 1995 to 22.9 grams in 2011/12 thanks to the popularity of diets that are typically lower in fibre such as fructose free (little or no fruit), gluten free (few grains), low-carb and paleo (few carbs at all) etc.
The food industry has stepped up to the proverbial plate, and is adding back, or enhancing, the amount of fibre in processed foods – often by adding in isolated or synthetic dietary fibres. This helps companies make positive nutrition claims like “high in fibre” or “good source of fibre”, and achieve a higher health star rating. Dietary fibre is a criterion for many nutrition profiling tools such as those used in Australia’s health claims system and the increasingly popular Health Star Rating System where more fibre generally means more stars.
However, will the simple addition of isolated or synthetic dietary fibres to processed foods make them as healthy as foods that are naturally good sources of dietary fibre like fruit and veg and legumes? The answer is we really don’t know yet – there are many different types of fibre and we do not know if all are truly beneficial. And perhaps dietary fibre is just a marker for an all-round healthy diet that does have lots of fruit and veg and legumes?
With this in mind, the US Food and Drug Administration have recently narrowed its definition of dietary fibre. The new rule defines “dietary fiber” as “non-digestible soluble and insoluble carbohydrates (with 3 or more monomeric units), and lignin that are intrinsic and intact in plants” and “isolated or synthetic non-digestible carbohydrates (with 3 or more monomeric units) determined by FDA to have physiological effects that are beneficial to human health such as lowering blood glucose and cholesterol levels, increasing feelings of fullness (satiety) resulting in reduced calorie [kilojoule] intake, and improving bowel function.”
The definition specifies that the following isolated or synthetic fibers have been determined by FDA to have physiological effects beneficial to human health: β-glucan soluble fiber, psyllium husk, cellulose, guar gum, pectin, locust bean gum and hydroxypropylmethylcellulose. FDA intends to publish a separate notice to seek comments and evaluate the scientific data on inulin, oat fiber, soy fiber, pea fiber, wheat fiber, sugar cane fiber and sugar beet fiber, amongst others.
Hopefully other food regulatory agencies around the world will follow the FDA’s lead to ensure only proven beneficial dietary fibres are added to our food supply.
Alan Barclay PhD is a consultant dietitian and scientific editor of GI News (*protected email*). He worked for Diabetes Australia (NSW) from 1998–2014 and is a member of the editorial board of Diabetes Management Journal (Diabetes Australia). He is author/co-author of more than 30 scientific publications, and co-author of The Low GI Diet: Managing Type 2 Diabetes (Hachette Australia) and The Ultimate Guide to Sugars and Sweeteners (The Experiment, New York). His new book, Reversing Diabetes (Murdoch Books Australia), was reviewed in Glycosmedia Diabetes News